1. Field of the Invention
The present invention relates to a process wherein beta-pinene is converted to perillyl alcohol and alpha-pinene is converted to trans-carveol.
The conversion process steps are substantially identical for both products. The process comprises the addition of benzoyl peroxide to beta-pinene or to alpha-pinene, catalyzed by cuprous ion, to form respectively perillyl benzoate or carveyl benzoate, followed by alkaline hydrolysis to form the respective alcohols. Yields are good, usually from about 60% to about 77%, based on benzoyl peroxide and a 2:1 to 5:1 ratio of pinene to benzoyl peroxide.
The instant invention resulted from experimental efforts to develop a process to meet the need for a less expensive perillyl alcohol and carveol for use in perfume blends. Prior to the present invention the high cost of these alcohols prohibited their use in any but the most expensive perfumes, and advantage could not be taken of their valuable odor, which makes them important as a lavandin extender in perfume blends suitable for soaps and detergent compositions.
2. The Prior Art
As early as Mar. 7, 1911 the art was apprised of the utility of pinene as a starting material for the production of another perfume substance with the issuance of U.S. Pat. No. 986,038, which describes the conversion of pinene to borneol.
U.S. PaT. No. 2,340,294, which issued on Feb. 1, 1944 relates to the reaction of beta-pinene with formaldehyde to form a dicyclic primary alcohol.
Processes for making perillyl alcohol and carveol have been known, but those processes have provided relatively poor yields, i.e., not over about 45%. For example there is described in Chem. Abs. 68, 87418t (1968), referring to British Pat. No. 1,094,875, a process wherein beta-pinene is oxidized by lead compounds in the presence of a fatty acid dissolved in glacial acetic acid to perillyl acetate, which is hydrolyzed to perillyl alcohol. The yield in this reaction is 45%.
Similarly reference is made to Chem. Abs. 63, 4335f (1965) and Chem. Abs. 64, 9776b (1966) wherein beta-pinene is oxidized with Pb.sub.3 O.sub.4 in glacial acetic acid to form perillyl alcohol.
Japanese Pat. No. 20,177 describes the synthesis of perillyl alcohol involving oxidation by lead tetraacetate. Yield is 45% based on beta-pinene.
The oxidation reaction with benzoyl peroxide is known as applied to the lower molecular weight olefins. For example J. K. Kochi, in J. Am. Chem. Soc. 84, 1572 (1962) describes a process of reacting butene-1 and butene-2 with benzoyl peroxide, in the presence of cuprous halides and cupric benzoate, at about 65.degree. to 75.degree.C for 24 hours. The conversion of butene-1 and butene-2 to C.sub.4 benzoates by the reaction described by Kochi involves a carbon-hydrogen homolytic cleavage.